He claims betting on the Knicks as a kid led to his gambling addiction — and now rooting the club on at one of its rare playoff games might have helped land wealthy Manhattan art dealer Hillel “Helly” Nahmad in jail.

Manhattan federal Judge Jesse Furman on Wednesday sentenced the son of billionaire art dealer ­David Nahmad to a year and a day behind bars as a major player in a $100 million international gambling ring that drew celebrities like Leonardo DiCaprio and Alex Rodriguez.

The 35-year-old scion of a family worth $3 billion also agreed to fork over $6.4 million in restitution and the rights to the 1937 painting Carnaval à Nice by American artist Raoul Dufy.

Nahmad told the judge that he was ashamed of letting his lifelong gambling habit cross a legal line.

“My family is a private family and I brought dishonor to it,” Nahmad told the judge in a courtroom packed with supporters. “I will never forgive myself for what I have done.”

Under federal sentencing rules, adding one day to the one-year sentence allows Nahmad to qualify for less time with good behavior. He was ordered to surrender by June 16.

“The record here before me reveals that the defendant has contempt for the law — and that he believes the rules apply to everyone else,” Furman said.

Before pronouncing sentence, the judge cited a photo of Nahmad sitting center court at a Knicks game, published in The Post on May 3, 2013. It was just weeks after Nahmad was indicted for running the gambling ring, which had ties to the Russian mob, from his $21.7 million Trump Tower condo.

Free on $10 million bail, he could be seen cheering hard with lawyer Benjamin Brafman, with Spike Lee two seats away. And he was sporting a Bicycle Playing Cards cap with a “King” card emblazoned on it.

In arguing Nahmad should serve a minimum of a year in prison, prosecutors said the scene suggests he was “making light of the seriousness of the gambling charges.”

Brafman argued Nahmad should get only probation because he had an otherwise clean record. The lawyer also claimed Nahmad got hooked on gambling by age 14, using a bookie to bet on Knicks games.

Furman quipped that it’s “not a crime to go to a Knicks game” — even though they “might not be good.” But he also said it “struck” him as “surprising” that Nahmad would wear the cap.

Brafman said he was to blame for convincing a “depressed” Nahmad to attend the game to lift his spirits.

Furman also sternly noted that wiretap evidence showed that Nahmad wasn’t just “the rich kid who is getting used.”

In one conversation, Nahmad discussed booking bets with someone who had just gotten out of a rehab clinic. “We knock this guy off for one million bucks,” Nahmad said. “His dad is a multimillionaire.”

Nahmad ran the high-stakes ring with reputed Russian mobster Illya Trincher, 53, catering primarily to millionaire and billionaire clients, the feds charged. Their business relied on several online illegal gambling websites to generate tens of millions of dollars of sports bets since 2012.

Trincher, 53, of Manhattan, faced a harsher fate as the judge hit him with five years behind bars — nearly double the guideline for his plea deal.

Nahmad had asked for probation so he could remain free to run his Manhattan art gallery and repay his debt to society by teaching art to underprivileged children.

But Furman said he believed that if Nahmad was really interested in giving back to others he would have began such a program long before he was sentenced.

Nahmad’s lawyers have said the conviction won’t impact operations at the Helly Nahmad Gallery at the Carlyle Hotel— a seller of exquisite works by Chagall, Warhol and other top artists.

The feds say the gambling ring was led by legendary Russian gangster Alimzhan Tokhtakhounov, who helmed the operation from overseas. Already wanted for trying to fix skating competitions at the 2002 Olympics, he has eluded capture for years despite extradition attempts.